1. Field of the Invention
The invention relates generally to the Schottky diode devices. More particularly, this invention relates to a device configuration and method of manufacturing Schottky diodes with a bottom-anode for multiple applications.
2. Description of the Prior Art
Conventional Schottky diodes with a vertical structure that has the cathode disposed at the bottom of a substrate are limited by several difficulties of applications. As a high voltage bias is applied to the substrate, the vertical Schottky diodes with cathode at the bottom of the substrate are not compatible with some assembly configurations. Furthermore, for high voltage devices, such device configuration requires an electrical isolation of the heat sink where the die is mounted, which causes limitations on heat dissipation and adds to complications to system designs when the vertical Schottky diodes are provided with the cathode disposed at the bottom of a substrate. Different types of vertical Schottky diodes have been disclosed. FIG. 1A shows a cross sectional view of a junction barrier Schottky diode formed on the top of a substrate and FIG. 1B shows an alternate Schottky diode implemented as a trench MOS-barrier Schottky diode on the top of a substrate. In either of the Schottky diodes, the Schottky barrier regions are shielded off laterally by depletion of the PN junctions or the MOS trenches when reverse bias reach a certain high voltage to reduce the leakage current. FIGS. 1C and 1D show alternate junction barrier Schottky (JBS) diodes in U.S. Pat. No. 4,134,123 with the P+ regions pinching off the drain from the top anode region. However, the Schottky diodes with a vertical configuration and the cathode on the bottom as shown in these disclosures are still limited by the difficulties discussed above for some practical applications, especially when applied to portable devices that require small package with multi functions to reduce component count and space. Specifically, for power boost converter application as showed in FIG. 1E, the anode of a Schottky diode is connected to the Drain of a MOSFET, which is usually at the bottom of the MOSFET die. It is desirable to co-package the Schottky diode into the MOSFET package to reduce anode parasitic inductance; it is necessary to have two separate die pads for mounting the MOSFET and the Schottky separately. This increases the assembly complexity and cost.
Therefore, a need still exists in the art of device design and manufacture of Schottky diodes by leveraging existing Schottky contact metallization schemes to provide new device configurations and manufacturing method for new and improved Schottky diodes with anode on the bottom of the substrate such that the above discussed problems and limitations can be resolved.